" It starts at reception and regardless of a change in circumstance the school continues to receive this money for the next 6 years. "
This is true of the generic Pupil Premium Grant (PPG), but for children adopted from care after 2005, they will receive Pupil Premium Plus (PPP) from reception until the end of Y11, regardless of any change in circumstance. The school will only receive the money whilst the child is on roll.
"It is up to the school how the money is spent however this must be published on the school website."
Again, this is true for the PPG, but the PPP MUST be spent to raise the attainment of the individual child. Whilst it is not technically ringfenced, schools will have to prove to Ofsted how they have used the money to raise the attainment of individual children. They should agree how to spend it with parents.
The Sutton Trust/EEF toolkit is a great resource to reference when deciding how to spend the PPP.
The school apply for the money via the school census, so there is a cut off date by which you should notify them of your child's status. Check with the school for timings.